The present invention relates an apparatus for continuously drying vegetables, particularly leaf vegetables.
More particularly, the invention, concerns an apparatus of the above kind, which allows the continuosly drying at high speed of delicate products, that could not be dried with the traditional centrifugation methods. As it is well known, in the last years an always large diffusion of the packaged vegetables commercialization occurred, said vegetables being already washed and ready to use by the consumer, particularly baby-leaf, lettuce heart, baby spinach, cresson, etc.
This diffusion determined the need of carrying out an optimum drying of the vegetables after its washing, before the packaging.
To this end, it is evident that there is a need to have an apparatus available to carry out a continuous step having a very high production rate.
In this field, it is included the solution,according to the present invention suggesting a new drying system realized in order to reduce the presence of free water on the whole or cut vegetable leaves, sold fresh within film bags, having a shelfxe2x80x94life of about 1-2 weeks when preserved within a refrigerator at a temperature of +4xc2x0 C., usually known as 4xc2x0 gamma products.
These and results are obtained, according to the present invention suggesting an apparatus providing two sections for the separation of the free water and comprises a first mechanical drying step and a second thermodynamic drying step.
It is therefore specific object of the present invention an apparatus for continuously drying vegetables, particularly leaf vegetables, comprising a mechanical drying section and a thermodynamic drying section, said mechanical drying section comprising a preliminary dripping section and a water removal section, or de-watering section, and said thermodynamic drying section comprising a hot section and a cold section.
Particularly, according to the invention, said preliminary dripping section comprises a conveyor belt on a vibrating section having variable dimensions.
More specifically, said conveyor belt is a plastic material belt of the xe2x80x9cmonofiloxe2x80x9d kind.
Furthermore, according to the invention, said water removal section or de-watering section comprises a structure, preferably made up of steel, a monofilo lower belt with a vibration system in its initial section, a first high rate vacuum pump, for sucking water separated from the product due to the, vibrations and to the upper ventilation effect, a monofilo upper belt, preferably comprised of a metallic or plastic net, a second high rate vacuum pump, for sucking the separated water from the product, due to the vibrations and the upper ventilation effect, three upper fans, provided with adjustable flaps to adjust air flows and the consequent motion of the products, and collection means for the removed water.
Preferably, according to the invention, upper protection means can be provided, said means being provided with inspection porthole of the upper part.
Further, according to the invention, means for the adjustment of the distance between said two belts can be provided, the adjustment occurring in function of the kind of product to be worked.
Still according to the invention, said water removal action can be realized by mechanical action, employing pre-heated air or de-humidified air.
Always according to the invention, said hot section of the thermodynamic drying section provides a recirculation air operation.
Preferably, according to the invention, said hot section provides a hot water of vapor operated battery having an air process temperature adjustment probe, acting on a motorized valve feeding the heating fluid with a constant air flow rate, a de-humidification unit, preferably provided with an automatic device for the energetic saving with the switching from outer air operation mode (winter mode) to recirculation air operation condition (summer mode), a drying bed, preferably comprised of three overlapped conveyors, each one provided with electronic speed variator, preferably having a Vmax/Vmin ratio of 4, exchange batteries, assembled within an air treatment console, comprising a heat regenerator, allowing an energy saving of about 40% on both air flows, evaporated water condensation occurring on one battery, said battery being fed by glicolated water, of with other refrigerating fluid, at a temperature of xe2x88x921xc2x0 C./0xc2x0 C., while on the other battery the heating of the air flow to the temperature required by the process, is carried out, a PLC controlled automatic system, as well as temperature, flow rate and humidity meters being provided, the ventilating section of the hot section being comprised of a centrifugal fan.
Preferably, said conveyor belts are made up of monofilo synthetic material, having the larger open surface and hole diameter compatible with the product to be worked, said conveyor belts being mounted overlapped on a common structure and placed within a insulated stainless steel structure, precisely made realized in order to prevent by-pass.
Still according to the invention, said drying process occurs counter-current, with the feeding of the product laterally from above and entrance of air from the opposite bottom side.
Particularly, according to the invention, the outer structure of the tunnel of the hot section is comprised of sandwich panels having a foamed polyurethane interspace, provided with stainless steel coating sheets.
Furthermore, according to the invention, air ejected from said hot section is collected by a stainless steel duct, to be conveyed to the cooling unit (condensation).
Always according to the invention, said cooling section is comprised of a xe2x80x9csingle passagexe2x80x9d tunnel, and is provided with a ventilating section comprising two helicoidal fans and two batteries fed by glicolated water, or any other refrigerating fluid, a conveyor belt provided with PLC controlled electronic speed variety,.an air dryer of the adsorption kind with silica-gel rotor, to reduce the condense content in the first part of the cooling section, and mechanical cooling means, comprising the second part of the cooling section.
Preferably, both the air temperature and the belt speed of the cooling section are adjustable.